/* 三角形 */
.comment-body > div{
  position: relative;
  left:3.67vw;
    content: "";
    width: 0;
    height: 0;
    border-bottom: 0.6rem solid  rgb(238, 238, 238);
    border-right: 0.6rem solid transparent;
    border-top: 0.1rem solid transparent;
    border-left: 0.6rem solid transparent;
}

 

效果(矩形上面的小三角形):